I would think that, rougly as Len has said, floods and flood zones are
more tangible things. They have canyons down which they come, and flood
zones that one can see (more or less) just by looking for the low spots.

But fire is purely an invisible statistical risk. There's no strictly
identifiable zone, although there are places where, like floods, it's
obvious if a fire starts below you, you can kiss your keester goodbye.

So, for floods, people have to rely less on their imagination. But this is
fascinating from a risk assessment standpoint. Traditionally, people are
more afraid of the less likely event. People are terrified of Firestone
tires which may have killed 100 people, but no similar fear exists of
driving in general which kills 50K per year. The same holds for mountain
lions. There are about 60 documented deaths by lion attacks in the last
100 years. There are a similar number of deaths by lightning strikes each
year. But what do people fear and react to? You guessed it.

That might give us a clue as to what people will prepare for: fire or
flood. The one less likely, the one more tangential to their lives, the
one where gambling seems a likely winner, is the one people will react to.